1. Field of the Invention
The present invention relates to a magnetic head including a recording part that performs recording of information to a magnetic recording medium, a reading part that performs reading of information, a recording part expansion heater, and a reading part expansion heater.
2. Description of the Related Art
In the field of magnetic recording using a magnetic head and a magnetic recording medium, along with the advancement of high recording density of a magnetic disk apparatus, further improvement in the performance of the magnetic head and the magnetic recording medium is demanded. As the magnetic head, a composite-type thin film magnetic head is widely used having a structure in which a reading part that includes a magnetoresistive (MR) element for reading and a recording part that includes an induction-type electromagnetic transducer element (magnetic recording element) for writing are laminated on a substrate. In the magnetic disk apparatus, the magnetic head is provided in a slider that flies slightly above a surface of the magnetic recording medium. The reading part and the recording part are prepared in a manner to be exposed on an air bearing surface (ABS) of the magnetic head that opposes the magnetic recording medium.
It is preferable that a distance between the magnetic recording medium and the recording part when recording information by using such a magnetic head and a distance between the magnetic recording medium and the reading part when reading information are respectively small and highly accurate. Therefore, for example, a configuration is disclosed in JP2006-351115A in which resistive heating bodies are respectively prepared in the vicinity of a recording part and the vicinity of a reading part, and, by using the two resistive heating bodies that are driven independently of one another, it is possible to respectively bring the recording part, when recording, and the reading part, when reading, close to the magnetic recording medium. According to this configuration, by respectively adjusting driving powers supplied to the resistive heating bodies, the distance between the recording part and the magnetic recording medium, when recording, and the distance between the reading part and the magnetic recording medium, when reading, can be finely adjusted.
On the other hand, in a magnetic recording device, along with the advancement of high density in magnetic recording, so-called thermally-assisted magnetic recording is proposed in which a magnetic material with large magnetic anisotropy energy Ku is used as a recording medium and a magnetic field is applied to perform writing after a coercive force is reduced by applying heat to the magnetic recording medium. In the thermally-assisted magnetic recording, a method in which laser light is used in order to apply heat to the magnetic recording medium is common. Among such methods, a method (near-field light heating) is proposed in which the laser light is converted to near-field light and the magnetic recording medium is heated by irradiating the magnetic recording medium with the near-field light. The near-field light is a kind of electromagnetic field that is formed around a substance and has a property that a diffraction limit due to the wavelength of the light can be ignored. By irradiating a microstructure body with light having aligned wavelengths, near-field light that depends on the scale of the microstructure body is generated and focusing of the light to a minimum region of about several tens of nm is possible.
As a specific means to perform thermally-assisted magnetic recording using near-field light, a thermally-assisted magnetic recording head using surface plasmons is proposed in JP2005-116155A. In this thermally-assisted magnetic recording head, instead of being directly radiated to a plasmon antenna, propagation light that propagates through a waveguide couples with a plasmon generator in a surface plasmon mode via a cladding layer. The light propagating through the waveguide is totally reflected at an interface between the waveguide and the cladding layer. In this case, light that is referred to as evanescent light and exudes to the cladding layer is generated. The evanescent light and collective oscillations of electric charges in the plasmon generator are coupled and surface plasmons are excited in the plasmon generator. The excited surface plasmons propagate to a near-field light generation end surface that is an ABS side end part of the plasmon generator, and near-field light is generated at the near-field light generation end surface. When the magnetic recording medium is irradiated with the near-field light, temperature in the recording part itself that performs the thermally-assisted magnetic recording (in particular, in the plasmon generator on which light is focused) also is likely to rise. That is, it is possible that not only heat generation of a recording part expansion heater and a reading part expansion heater, but also the irradiation of the near-field light can cause temperature rise and thermal expansion in the magnetic head that performs the thermally-assisted magnetic recording.
In order to minimize capacity loss of the magnetic recording medium (HDD), it is desirable that the reading part and the recording part be arranged close to each other at the ABS of the magnetic head. However, when the reading part and the recording part are close to each other, there is a possibility that, when the resistive heating body in the vicinity of the reading part is driven during reading, temperature rise and expansion also occur in the recording part. In this case, the recording part that is generally positioned on a trailing side becomes in contact with the magnetic recording medium before the reading part does, and thus the reading part is prevented from becoming further closer to the magnetic recording medium. Therefore, there is a possibility that it is difficult to have a desired distance between the reading part and the magnetic recording medium. It is not preferable to increase the distance between the recording part and the reading part at the ABS in order to prevent that temperature rise also occurs in the recording part when the reading part is heated, because the capacity loss in the HDD will increase.
In particular, in order to perform accurate reading of information, it is important that the distance between the reading part and the magnetic recording medium be accurately set smaller. Usually, when setting a flying height of a slider (distance between the slider and the magnetic recording medium), at least once the ABS is brought into contact with the magnetic recording medium (or its substitute) and then the flying height from the magnetic recording medium, that is, the distance between the ABS and the magnetic recording medium, is adjusted. Therefore, in order to adjust the distance between the reading part and the magnetic recording medium, the reading part has to be brought into contact with the magnetic recording medium. Suppose that the recording part or its vicinity is brought into contact with the magnetic recording medium before the reading part is brought into contact with the magnetic recording medium, the reading part cannot be brought into contact with the magnetic recording medium, and the flying height from the magnetic recording medium has to be set based on the position where the recording part or its vicinity and the magnetic recording medium are in contact with each other. Therefore, the distance between the reading part and the magnetic recording medium cannot be accurately set.